Notes

CHAPTER 1

1.I owe much of the embryological detail described in this chapter to Essentials of Human Embryology by William J. Larsen (New York: Churchill Livingstone, 1998).

2.I discuss the evolution and development of sea squirts and lancelets, and their relationship to backboned animals, in my book Before the Backbone (London: Chapman & Hall 1996).

3.The earliest-known vertebrates are the fossils of fish-like creatures from China that lived some 530 million years ago (see the paper by De-Gan Shu, Hui-Lin Luo, S. Conway Morris, Xing-Liang Zhang, S.-X. Hu, Liang Chen, J. Han, Min Zhu and L.-Z. Chen, Nature, vol. 402, 1999, pp. 42–6). However, we have no way of knowing whether these particular fossils were our lineal ancestors.

4.Estimates of the numbers of species on Earth at present vary enormously, from around 1.4 million to 200 million.

5.For more about the lives of the remarkable Rothschilds, see Dear Lord Rothschild: Birds, Butterflies, and History by Miriam Rothschild (Glenside, Pennsylvania: Balaban, 1983) and The English Rothschilds by Richard Price Davis (Chapel Hill: University of North Carolina Press, 1983).

CHAPTER 2

1.The background to the early history of embryology as described in this and the next chapter, including preformationism and much else of interest, can be found in Early Theories of Sexual Generation by F. J. Cole (Oxford: Clarendon Press, 1930), A History of Embryology by Joseph Needham (Cambridge: Cambridge University Press, 1934), Investigations into Generation 1651–1828 by Elizabeth B. Gasking (London: Hutchinson, 1967) and a sparkling recent book, The Ovary of Eve, by the biologist, poet and novelist Clara Pinto-Correia (Chicago: University of Chicago Press, 1997).

2.Quoted in Needham, op. cit., p. 48, and attributed to Charles Singer.

3.Ibid., p. 49.

4.Ibid., p. 50.

5.‘Cell theory’ as we know it today was a product of the nineteenth century, but its first stirrings – in the idea that organisms were divisible into small units called ‘cells’ – lay the other side of the Restoration, with the publication in 1665 of Micrographia by the English microscopist Robert Hooke (1635–1703), who described the cells of cork wood.

6.For more on Harvey’s insight see the essay ‘Where do babies come from?’ by R. V. Short, Nature, vol. 403, 2000, p. 705.

7.Gasking, op. cit., p. 43.

CHAPTER 3

1.This is quoted on p. 2 of F. J. Cole’s Early Theories of Sexual Generation (Oxford: Clarendon Press, 1930). Cole gives a date of 1678 for Huygens’s statement, but no attribution is given for Cole’s translation, which he may have done himself.

2.The concept of ‘fertilization’, as distinct from fecundation, depends on the union of egg and sperm. Spallanzani did not believe that sperm had any role in generation, so the term ‘fertilization’, in the sense of generation, would have had no meaning for him.

3.Elizabeth B. Gasking, Investigations into Generation 1651–1828 (London: Hutchinson, 1967), p. 132.

CHAPTER 4

1.Quoted by Elizabeth B. Gasking, directly from Wolff’s Theoria generationis, on p. 103 of Investigations into Generation 1651–1828 (London: Hutchinson, 1967).

2.Ibid.

3.Robert J. Richards gives a good, brief account of the ideas of the nature-philosophers in The Meaning of Evolution (Chicago: University of Chicago Press, 1992). The quote from Lorenz Oken is from this source (p. 39), translated from Oken’s Abriss des Systems der Biologie (Göttingen: Vandenhoek und Ruprecht, 1805). Richards’s account is given in the context of Darwin’s early ideas of progressive evolution, before natural selection took shape.

4.The scientific works of Goethe are conveniently available in English, in Goethe: The Collected Works, Volume 12 – Scientific Studies, edited and translated by Douglas Miller (Princeton: Princeton University Press, 1988).

5.See an article by Günter Theissen and Heinz Saedler, Nature, vol. 409, 2001, pp. 469–71.

6.This idea is an important part of the thinking of the twentieth-century philosopher Rudolf Steiner (1861–1925), whose ‘anthroposophy’ draws heavily on the works of Goethe and on nature-philosophy in general. The preoccupation of anthroposophists with holism, the interrelationships between body and spirit, and general ecological concerns, can all find their roots in Goethe and in nature-philosophy more generally. Anthroposophists also promote some of Goethe’s more outmoded concepts such as his theory of colour, concentrating on its aesthetic rather than its scientific value.

7.This quote comes from Douglas Miller, op. cit., p. xxi.

8.The debate between Cuvier and Geoffroy, and the context in which the debate was set (including the meeting between Soret and Goethe) is described in The Cuvier – Geoffroy Debate: French Biology in the Decades before Darwin by Toby A. Appel (New York: Oxford University Press, 1987). It is a shame that this marvellous book is unread outside academia. Somebody should make it into a film.

9.Today, nobody believes that the skull has any particular relationship with vertebrae. The head seems to be a structure developmentally and morphologically unrelated to vertebrae. The braincase and parts of the base of the skull are made of cartilage separate from the cartilages that form the vertebrae: the jaws, face and much of the superficial bones of the skull are derived from neural crest cells.

10.Amazingly, recent work in comparative developmental genetics has suggested that GeofFroy’s far-fetched ideas contain more than a grain of truth. The genes that in vertebrates direct the formation of dorsal structures, such as the spinal cord, have evolutionary correspondents in insects that organize the ventral ectoderm, and vice versa. This has led some workers to posit a wholesale inversion of vertebrate structure (with respect to insect structure) very early in animal evolution. (See ‘Inversion of dorsoventral axis?’ by D. Arendt and K. Niibler-Jung, Nature, vol. 371, 1994, p. 26; and ‘A common plan for dorsoventral patterning in Bilateria’ by E. M. De Robertis and Y. Sasai, Nature, vol. 380, 1996, pp. 37-40.)

CHAPTER 5

1.Perhaps the most readable account of the life of Charles Darwin is Darwin, by Adrian Desmond and James Moore (London: Penguin, 1992). The history of evolution as well as genetics is told in breezy style by historian David L. Hull in Science as a Process (Chicago: University of Chicago Press, 1988).

2.The effort was vain: Fitzroy eventually killed himself.

3.I am indebted to Jack Cohen, who pointed out to me that profligate waste is the natural order of animal and plant reproduction: see his essay in Nature, vol. 411, 2001, p. 529.

4.Hull, op. cit., p. 40.

5.This now cliché’d quote appears in a letter from Darwin to Joseph Hooker written in 1871, published in Francis Darwin (editor), The Life and Letters of Charles Darwin, vol. 3 (London: John Murray, 1888), p. 18.

6.Paracelsus, Das Buch von der Gebärung der Empfindlichen Dinge in der Vernunfi (c.1520), vol. I, section i, pp. 261–2, cited on p. 59 of Paracelsus: Essential Readings, edited and translated by Nicholas Good-rick-Clarke (Berkeley, California: North Atlantic Books, 1999). I am grateful to Philip Ball for discovering this and other alchemical arcana.

7.Quoted on p. 131 of Elizabeth Gasking, Investigations into Generation 1651–1828 (London: Hutchinson, 1967) from L. Spallanzani, Tracts on the Natural History of Animals and Vegetables, translated by J. Dalyell (Edinburgh, 1803).

8.F. J. Cole, Early Theories of Sexual Generation (Oxford: Clarendon Press, 1930), p. 176.

9.See my essay ‘Aspirational thinking’ (Nature, vol. 420, 2002, p. 611). The late Stephen Jay Gould was fond of exposing the conceits of progressive, destiny-driven evolution, as shown by his collection of man-from-the-apes commercials in Wonderful Life (New York: Norton, 1989).

10.I discuss this issue in depth on my book In Search of Deep Time (New York: Free Press, 1999), published in the UK as Deep Time (London: Fourth Estate, 2000).

11.Form and Function: A Contribution to the History of Animal Morphology by E. S. Russell (London: John Murray, 1916) is a typical example of a work written when disenchantment with Darwinism was at its deepest. Russell advocates a Lamarckian model of evolution and mentions with approval the work of Samuel Butler (1835–1902), the author of Erewhon and The Way of All Flesh, who was a prominent anti-Darwinian of the period. This is the same Butler whose views, along with those of Paley, were disparaged by Bateson in Materials for the Study of Variation. Despite Russell’s views on evolution – which are, of course, nowadays seen as quite outmoded – Form and Function is a classic text on morphology, still cited today.

12.From the preface to W. Bateson, Materials for the Studies of Variation treated with Especial Regard to Discontinuity in the Origin of Species (London: Macmillan, 1894), p. v.

CHAPTER 6

1.See Nature, vol. 122, 1928, pp. 339–40; see also the anonymous obituary of Bateson in Nature, vol. 117, 1926, pp. 312–13.

2.See Nature, vol. 124, 1926, p. 171.

3.For more about the history of research into the origin of vertebrates, see my own book Before The Backbone (London: Chapman & Hall, 1996) The debate about vertebrate ancestry that took place at the Linnean Society appears in full in Gaskell, W. H. et al., ‘Discussion on the origin of vertebrates’, Proceedings of the Linnean Society of London, session 122 (1909-1910), 1910, pp. 9-50. I am grateful to Stuart Baldwin for unearthing this gem for me.

4.Quoted from Gaskell et al., op. cit..

5.From the preface to W. Bateson, Materials for the Studies of Variation treated with Especial Regard to Discontinuity in the Origin of Species (London: Macmillan, 1894), p. vi.

6.Ibid.

7.Ibid., p. 570.

8.Ibid., p. 147.

9.Ibid., p. 148.

10.Ibid., p. 568 (emphasis in original).

11.Ibid., p. 573. 257 Jacob’s Ladder

12.Quoted on p. 53 of David L. Hull, Science as a Process (Chicago: University of Chicago Press, 1988).

CHAPTER 7

1.See The Monk in the Garden: The Lost and Found Genius of Gregor Mendel, the Father of Genetics by R. M. Henig (Boston: Houghton Mifflin, 2000).

2.Both J. B. S. Haldane (Nature, vol. 122, 1928, pp. 339-40) and Thomas Hunt Morgan (Nature, vol. 124, 1926, pp. 171-2) had views on what really happened when Bateson had his eureka moment on a train in 1900. Haldane implies that Bateson actually read Mendel’s paper on the train, whereas Morgan suggests that Bateson had only read the paper by De Vries in which Mendel’s work was mentioned. The account here – that Bateson had received De Vries’s paper and then looked up Mendel – is the one given by David Hull in Science as a Process (Chicago: University of Chicago Press, 1988).

3.The life and works of Morgan are described in Thomas Hunt Morgan, Pioneer of Genetics by Ian Shine and Sylvia Wrobel (Lexington: The University Press of Kentucky, 1976).

4.Hence the popular scientific in-joke that time flies like an arrow, but fruit flies like a banana.

5.Shine and Wrobel, op cit.

6.It is possible that Mendel did not publish results that were less clear cut, but this may now be difficult to say given the destruction of many of his papers after his death.

7.W. S. Sutton, ‘The chromosomes in heredity’, Biology Bulletin, vol. 4, 1903, pp. 231–51.

8.There may even be more than one split point, but I confine my discussion to just one split point in each chromosome, to avoid it becoming more complicated than it needs to be.

CHAPTER 8

1.Myoglobin is the substance that carries oxygen within muscles, and is distinct from the haemoglobin that does the same job in the blood, although they are chemically related.

2.James D. Watson, The Double Helix (London: Penguin, 1999). This recent edition has an introduction by geneticist Steve Jones.

3.Walter Gratzer, A Bedside Nature: Genius and Eccentricity in Science 1869-1953 (London: Macmillan Magazines, 1996). 258 Notes

4.J. D. Watson and F. H. C. Crick, ‘A structure for deoxyribose nucleic acid’, Nature, vol. 171, 1953, p. 737. Ever since this paper was published, whenever a Nature editor sees a line in a manuscript beginning ‘It has not escaped our notice . . .’ it is almost always remorselessly deleted.

5.An issue of Nature (vol. 421, 2003, pp. 396–453) commemorating the fiftieth anniversary of these events contains facsimiles of the Watson – Crick paper, as well as others which appeared at the time, and other material of interest exploring the scientific and cultural ramifications of the discovery of the structure of DNA.

6.See F. H. C. Crick, Leslie Barnett, S. Brenner and R. J. Watts-Tobin, ‘General nature of the genetic code for proteins’, Nature, vol. 192, 1961, pp. 1227-32.

7.Given the enormous differences between viruses and bacteria, it is exceedingly unfortunate and breathtakingly inappropriate that they tend to be grouped together (with any other microscopic organism) as bugs. The word ‘bug’ can be applied with justification to an insect of the order Hemiptera, a river in Eastern Europe, and, possibly, an unintended feature of a computer program. It should, however, not be applied to a microorganism, under any circumstances whatsoever, and anyone who uses the term in this sense is guilty of the kind of sloppy journalism that induces newsreaders (who are as routinely and shamefully ignorant of science as they are well-informed about politics) to use the terms ‘virus’ and ‘bacterium’ as if they were interchangeable – or worse, to use the word ‘bacteria’ (or, for that matter, ‘criteria’ or ‘phenomena’) as a singular.

CHAPTER 9

1.A. E. Garrod, Inborn Errors of Metabolism (London: Henry Froude and Hodder & Stoughton, 1923).

2.Beadle, Tatum, and Tatum’s student Joshua Lederberg shared a Nobel prize in 1958 for their work.

3.This classic paper was published in the Journal of Molecular Biology, vol. 3, pp. 318-56, 1961.

4.The same lambda that hides out in the genome of strain K12λ, of the bacterium Escherichia coli.

5.As everyone who does the laundry knows, there is no better way to get your washing really clean than to hang it outdoors in the sunshine. Sunshine is rich in UV and is a potent natural anti-bacterial agent. 259 Jacob’s Ladder

CHAPTER 10

1.See the report by William Shawlot and Richard R. Behringer, ‘Requirement for Lim 1 in head-organizer function’, Nature, vol. 374, 1995, pp. 425-30.

2.For technical details on the homeo-box, see Guy Riddihough’s article ‘Homing in on the homeobox’, Nature, vol. 357, 1992, pp. 643–4, and references therein.

3.Confusingly, some genes have both paired- and homeo-boxes, so they are simultaneously members of the Hox and Pax families.

4.Lewis’s own account of his work can be found in ‘A gene complex controlling segmentation in Drosophila’, Nature, vol. 276, 1978, pp. 565-70.

5.Alexander Awgulewitsch and Donna Jacobs, ‘Deformed autoregulatory element from Drosophila functions in a conserved manner in transgenic mice’, Nature, vol. 358, 1992, pp. 341–5; andJarema Malicki, Luciano C. Cianetti, Cesare Peschle and William McGinnis, ‘A human HOX4B regulatory element provides head-specific expression in Drosophila embryos’, Nature, vol. 358, 1992, pp. 345-7.

6.J. Garcia-Fernandez and P. W. H. Holland, ‘Archetypal organization of the amphioxus Hox gene cluster’, Nature, vol. 370, 1994, pp. 563–6.

7.A. Amores et al., ‘Zebrafish hox clusters and vertebrate genome evolution’, Science, vol. 282, 1998, pp. 1711-14.

8.Sean B. Carroll, ‘Homeotic genes and the evolution of arthropods and chordates’, Nature, vol. 376, 1995, pp. 479-85.

9.The paper on gene regulation in fruit flies by Christiane Nusslein- Volhard and Eric Wieschaus was published as ‘Mutations affecting segment number and polarity in Drosophila’ in Nature, vol. 287, 1980, pp. 795-801.

10.20,000 was the total number of genes then thought to have been contained in the fruit fly’s genome. Subsequent work has shown that the total is far fewer, around 13,600.

11.See ‘Genetic control and evolution of sexually dimorphic characters in Drosophila’ by Artyom Kopp, Ian Duncan and Sean B. Carroll, Nature, vol. 408, 2000, pp. 553-9.

12.The paper on the network properties of the segmentation module is ‘The segment polarity network is a robust developmental module’, by Georg von Dassow, Eli Meir, Edwin M. Munro and Garrett M. Odell, published in Nature, vol. 406, 2000, pp. 188-92.

13.My favourite expression of the democratic, even subversive, anonym- 260 Notes ity of the internet – a consequence of the importance of the network over any of its components – is the well-known New Yorker cartoon in which two dogs sit in front of a monitor. ‘On the internet,’ says one, ‘no one knows you’re a dog.’

14.Actually, Lim 1-mutant mice lack kidneys and gonads, but this is not apparent from a superficial examination.

15.This is, of course, an oversimplification. Many single-celled creatures develop inasmuch as changes in their environments allow them to select their fates, such as whether a bacterium should continue to feed or encapsulate itself into a quiescent cyst, or whether a bacteriophage should remain virulent or become an inactive passenger in the genome of its host.

CHAPTER 11

1.K. Padian, ‘A daughter of the soil: Themes of deep time and evolution in Thomas Hardy’s Tess of the d’Urbervilles’, Thomas Hardy Journal, vol. 13, 1997, pp. 65-81.

2.See ‘Whole-genome shotgun assembly and analysis of the genome of Fugu rubripes’ by Samuel Aparicio and colleagues, Science vol. 297, 2002, pp. 1301–10; and the accompanying commentary, ‘Vertebrate genomes compared’ by S. Blair Hedges and Sudhir Kumar, Science, vol. 297, 2002, pp. 1283-5.

3.See E. G. Nisbet and N. H. Sleep, ‘The habitat and nature of early life’, Nature, vol. 409, 2001, pp. 1083-91.

4.To avoid cluttering up this chapter with footnotes to scientific reports on individual genomes, I refer the reader to the Nature online resource for genomics, http://www.nature.com/genomics/, as well as the online resource maintained by The Institute for Genomic Research (TIGR), http://www.tigr.org

5.See, for example, G. F. Joyce, ‘Booting up Life’, Nature, vol. 420, 2002, pp. 278-9; and S. A. Strobel ‘Repopulating the RNA world’, Nature, 2001, vol. 411, pp. 1003–6, and references therein.

6.Cairns-Smith’s ideas are explored in his book Seven Clues to the Origin of Life (Cambridge: Cambridge University Press, 1990) and in a chap ter, ‘The origin of life: Clays’, pp. 169–92, in Frontiers of Life, vol. 1, edited by D. Baltimore, R. Dulbecco, F.Jacob and R. Levi-Montalcini (New York: Academic Press, 2001). I am grateful to Professor Cairns- Smith for sending me a reprint of that chapter.

7.See R. D. Fleischmann and colleagues, ‘Whole-genome random 261 Jacob’s Ladder sequencing and assembly of Haemophilus influenzae Rd.’, Science, vol. 269, 1995, pp. 496-512.

8.I am not sure why, but I find the name Reclinomonas americana curiously attractive. It brings to mind 1950s kitsch and pop-art pieces such as the collage by Richard Hamilton entitled Just What Is It That Makes Today’s Homes So Different, So Appealing?

9.See R. Ainscough and colleagues, ‘Genome sequence of the nematode Caenorhabditis elegans: A platform for investigating biology’, Science, vol. 282, 1998, pp. 2012-18.

10.This total was far less than the 20,000 assumed by Nüsslein-Volhard and Wieschaus in their mutational experiments.

11.See note 3 of Chapter 1.

12.See ‘The draft genome Ciona intestinalis: Insights into chordate and vertebrate origins’ by Paramvir Dehal and colleagues, Science, vol. 298, 2002, pp. 2157–67; and ‘Return of a little squirt’, my commentary on this paper, in Nature, vol. 420, 2002, pp. 755-6.

13.See ‘A new hominid from the Upper Miocene of Chad, central Africa’ by Michel Brunet and colleagues, Nature, vol. 418, 2002, pp. 145-51.

14.See ‘Molecular evolution of FOXP2, a gene involved in speech and language’ by Wolfgang Enard and colleagues, Nature, vol. 418, 2002, pp. 869-72.

15.In his novel The Fountains of Paradise, Arthur C. Clarke jokes that religion is a by-product of the mammalian reproductive system.

16.See ‘Growth processes in teeth distinguish modern humans from Homo erectus and earlier hominins’ by Christopher Dean and colleagues, Nature, vol. 414, 2001, pp. 628-31.

17.See The Wisdom of Bones by Pat Shipman and Alan Walker (New York: Alfred A. Knopf, 1996) for a remarkable portrait of the life and times of Homo erectus.

CHAPTER 12

1.See ‘Genetic control and evolution of sexually dimorphic characters in Drosophila by Artyom Kopp, Ian Duncan and Sean B. Carroll, Nature, vol. 408, 2000, pp. 553-9.

CHAPTER 13

1.I have deliberately avoided making any connection between the evolution of sentience and the evolution of brains, because the evolution 262 Notes of sentience is not necessarily restricted to the evolution of brains. One can imagine structured societies similar to those of social insects – ants, bees and wasps – in which individuals have very small brains but sentience might arise as a consequence of their collective actions. This point is elegantly made by Douglas Hofstadter in Gödel, Eschar, Bach: The Eternal Golden Braid (London: Penguin, 1979).

2.See Sean Carroll’s article ‘Genetics and the making of Homo sapiens’, Nature, vol. 422, 2003, pp. 849-57.

3.See Jared Diamond’s article ‘The double puzzle of diabetes’, Nature, vol. 423, 2003, pp. 599-602.

4.See Gregory Stock’s book Redesigning Humans: Choosing our Children’s Genes (Boston: Houghton Mifflin, 2002).

5.In his article ‘Artificial wombs: An out of body experience’ (Nature, vol. 419, 2002, pp. 106–7), Jonathan Knight reports how technology to sustain life in early embryos is running in parallel with devices that can keep babies alive when born in an ever more premature condition. Perhaps, he wonders, the two efforts will meet in the middle and we shall have artificial wombs in which gestation can proceed entirely outside the human body. If this happens, human beings in their mode of reproduction will be no different from a chicken or any other animal that lays external eggs – a curious vindication of Harvey’s dictum.

6.The social consequences of elective genetic modification have provided a major theme in contemporary science fiction. As a genre, science fiction does not predict the future: rather, it provides the expression, in the context of the future, of current preoccupations about the impact of technology on society. Immediately after World War II, for example, SF was full of post-apocalyptic stories of worlds recovering from nuclear calamity, whereas today the genre is preoccupied with what people in the field call ‘posthumanity’. To celebrate the millennium, I ran a column in Nature called ‘Futures’ in which writers, almost all professional SF authors, were invited to explore, in the form of a short, fictional vignette, how technology might affect the way we live in the next millennium. ‘Futures’ ran from November 1999 to December 2000, and of the fifty-eight stories published, eleven explored the consequences of improvements in the technology of reproduction, including the modification of the human form, on ethics, politics, religion, personality and society. Only three stories involved direct contact with aliens – usually regarded as the SF staple – and one of those used aliens as a vehicle for comedy.